Turbomachines, such as those in turbofan, turbojet, and other turbine engines often experience forces during operation which can affect the clearances between operating components. For example, an aircraft can perform maneuvers during flight which cause bending in the components due to their inertia. To accommodate bending from normal operations, components of the aircraft engine have spacing between them. For example, an engine core having a rotating shaft with radial airfoils may be enclosed by a housing. To accommodate bending in the housing of the core, a space may be present between the airfoil tips and the housing. The components may be spaced apart further than they would otherwise to permit bending of the housing.
This spacing, also known as a clearance or tolerance, has the disadvantage of reducing the efficiency of the engine, or other turbomachine. In the example of the rotating shaft, air can travel around the airfoils by passing between the airfoils and the housing, rather than travelling over an airfoil, as desired. Accordingly, the efficiency of the engine is reduced as less work is extracted from the passing air by the airfoils.
A typical approach to reducing the required clearances between components is to couple the ends of the housing of the core of the engine to surrounding components, such as a bypass duct. Unfortunately, rotating elements within the core are not supported in the same way as the housing of the core. Thus, restraining the housing of the engine core can cause the housing of the engine core to bend around the central rotating shaft, which remains relatively straight. As a result, the airfoils will approach undesirably close to the interior of the housing.